1. Field of the Invention
The present invention relates to a vehicle periphery visual confirmation apparatus which, under a poor visibility condition, takes a picture of a peripheral scene before or behind a vehicle, or, a picture of the right-side or left-side scene oft he vehicle, that is, the scene of a blind spot to a driver, and displays the picture of such vehicle peripheral scene to the driver.
2. Description of the Related Art
FIG. 5 shows the structure of a conventional vehicle periphery visual confirmation apparatus. This vehicle periphery visual confirmation apparatus 1 comprises a picture camera apparatus 11 disposed on the outside portion of a vehicle to take pictures of two vehicle peripheral scenes existing in the mutually opposite directions, a mirror image reversal processing part 12 for mirror-image processing picture signals supplied from the picture camera apparatus 11, and a display part 15 disposed within a vehicle room for displaying the picture images obtained from the mirror image reversal processing part 12.
The picture camera apparatus 11 comprises: a lightproof case 3 on the two sides of which there are formed a pair of left and right penetration window portions 2L, 2R each made of transparent glass; a prism 4 having an isosceles-triangular-shaped section stored in the interior portion of the case 3 and disposed in such an attitude that its vertical angle portion 5 faces the front portion of the case 3 (in FIG. 5, the upper portion of the case 3) and its prism side surfaces 8L, 8R respectively face the left and right penetration window portions 2L, 2R; and, an imaging device 10 stored and disposed in the rear of the prism 4 for converting light rays 18L, 18R into image signals. Here, referring specifically to the light rays 18L, 18R, they enter the prism side surfaces 8L, 8R, their respective light paths are changed within the prism 4, and then they are guided through a given imaging lens 9 onto the imaging surface of the imaging device 10. In this structure, the imaging lens 9 is disposed in the rear of the prism 4 (in FIG. 5, in the lower portion) in such a manner that the optical axis 25 of the imaging lens 9 is coincident with the bisector of the vertical angle portion of the isosceles-triangular-shaped section of the prism 4.
The thus structured picture camera apparatus 11 is mounted on the front bumper or front grille of the vehicle in such a manner that, for example, the front portion of the picture camera apparatus 11 (the front portion of the case 3) faces forwardly of the vehicle and the penetration window portions 2R. 2L respectively face on the right and left sides of the vehicle.
In this state, the light ray 18L corresponding to the scene of the left side of the vehicle, as shown in FIG. 5, penetrates through the penetration window portion 2L and prism side surface 8L, advances through the interior portion of the prism 4 and reaches the prism side surface 8R. And, the light ray 18L is then internally reflected by the prism side surface 8R, is radiated from the prism side surface 8R, is image formed by the imaging lens 9, and is guided to the left half surface 10L of the imaging surface of the imaging device 10.
In the case of the light ray 18R which corresponds to the right-side scene of the vehicle, as the light rays 18L and 18R are symmetric, the light ray 18R is similarly guided to the right half surface 10L of the imaging surface of the imaging device 10. And, both of the light rays 18L, 18R are converted into image signals by the imaging device 10.
The pictures of the left-side and right-side scenes are taken in this manner, the image signals of the pictures are mirror image reversal processed by the mirror image reversal processing part 12, and, as shown in FIG. 6, are supplied to the display part 15. In the display part 15, the left-side scene taken in from the penetration window portion 2L is displayed on the left half screen 15L of the display part 15 as a left-side scene image 19L, whereas the right-side scene taken in from the penetration window portion 2R is displayed on the right half screen 15R of the display part 15 as a right-side scene image 19R.
However, in the conventional vehicle periphery visual confirmation apparatus, there is a fear that part of the other picture can come out in one picture, that is, an image like a vision (which is hereinafter referred to as a vision image) can appear, thereby degrading the visibility of the picture. For example, as shown in FIG. 5, let us assume a case in which, at night, a vehicle with a headlight 20 on approaches our vehicle slightly from the right side. In this case, after the light of the headlight 20 penetrates through the right-side penetration window portion 2R, part of the light passes through the adjacent portion of the vertical angle portion of the prism 4 and reaches the left-side penetration window portion 2L. Here, about 96% of the light that has arrived at the left-side penetration window portion 2L penetrates through the left-side penetration window portion 2L, whereas the remaining light 21, namely, about 3% of the light is reflected by the internal surface of the left-side penetration window portion 2L. As a result of this, the light 21 is allowed to enter the left-side prism side surface 8L. The light 21, which has entered the left-side prism side surface 8L in this manner, advances through the interior portion of the prism 4, reaches the right-side prism side surface 8R, and is reflected by the internal surface of the right-side prism side surface 8R; and, after then, the light 21 is radiated from the prism rear surface 8B of the prism 4, is image formed by the imaging lens 9, and is guided to the left half surface 10L of the imaging surface of the imaging device 10.
In other words, in the present case, the partial light 21 of the light from the headlight 20, which ought to be situated on the right side, is image formed by the imaging lens 9 while it is overlapped with the light ray 18L entering from the left side, and is guided to the left half surface 10L of the imaging surface of the imaging device 10; and, the thus-formed image is displayed on the left half screen 15L of the display part 15 as the left-side scene image.
The present invention aims at eliminating the above drawbacks found in the conventional vehicle periphery visual confirmation apparatus. Accordingly, it is an object of the invention to provide a vehicle periphery visual confirmation apparatus capable of preventing occurrence of a vision image which is caused when light entering from the outside through one of right and left penetration window portions passes through the adjacent area of the vertical angle portion of the right and left prism side surfaces of a prism and is then reflected by the opposite-side penetration window portion.
In attaining the above object, according to a first aspect of the invention, there is provided a vehicle periphery visual confirmation apparatus comprising a picture camera apparatus disposed on the outside of a vehicle, the picture camera apparatus comprising: a case including a pair of right and left penetration window portions respectively formed on the two sides thereof; a prism having an isosceles-triangular-shaped section and disposed within the case in such an attitude that its vertical angle portion faces the front portion of the case and its right and left prism side surfaces corresponding to the two equal sides of its isosceles triangle shape respectively face the right and right penetration window portions; and, an imaging device which is disposed in the rear of the prism and also which, when light rays entering from one of the right and left prism side surfaces are reflected by the other of the right and left prism side surfaces and are radiated from the prism rear surface of the prism, focuses the light rays onto an imaging surface of the imaging device through a given imaging lens to thereby convert the light rays into image signals, wherein, between the vertical angle portion of the prism and the front end wall of the case, there is interposed light shielding means for shielding light rays crossing substantially in the right and left direction in front of the prism.
According to a second aspect of the invention, in a vehicle periphery visual confirmation apparatus as set forth in the first aspect of the invention, the light shielding means is formed integral with the front end wall of the case.
According to a third aspect of the invention, in a vehicle periphery visual confirmation apparatus as set forth in the first aspect of the invention, the light shielding means is formed integral with a prism fixing member for fixing the prism to the case.